Road milling machine with optimized operation

ABSTRACT

A road milling machine having a milling roller with a plurality of chisels. A signal receiving unit is assigned to a machine component which is directly or indirectly involved in the milling process or to another machine component. The signal receiving unit detects an operating condition of the machine component and is connected to a signal emitting unit. An optical detecting device may be assigned to the road milling machine, whereby operations are made easier and the milling pattern is optimized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a construction machine, in particular forworking ground surfaces or for stripping traveled surfaces by a millingroller which has a multitude of chisels.

2. Discussion of Related Art

Construction machines are known, for example, as road milling machines.They have a milling roller equipped with a multitude of chisels, inparticular round-shaft chisels. The milling roller rotates duringoperation and the chisels engage with the ground covering to be worked.The chisels are subjected to continuous wear and must be replaced aftera defined time of operation. However, the service life of the chiselslargely depends on the milling conditions. Often, the machine operatorexchanges the chisels either too early or too late. If they are replacedtoo early, unnecessary tool expenses arise. If replaced too late, damageto the milling roller can occur.

A further problem in the milling process relates to premature chiseldrop-out. One or several chisels can break because of external effects,or because of tool irregularities. Then, no material is removed at theplaces where the chisel is positioned. In addition, the stress on theadjoining tools increases and the tools are subjected to greaterstresses.

Stabilizers, recyclers and trimmers are also known constructionmachines.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a construction machine ofthe type mentioned above, by which an optimized working operation can beperformed.

This object is achieved with a signal pickup unit that is assigned to amachine component, or another machine component which is directly orindirectly involved in the work process. The signal pickup unit detectsan operational status of the machine component, and the signal pickupunit is connected to a signal output unit via a signal processingarrangement.

One or if required, several machine component can be monitored by thesignal pickup unit. In the process, the operational status of themachine component is used as a parameter, or characteristic diagram. Thedetected parameters can be compared with a reference quantity or areference quantity diagram. As soon as an inadmissible deviation occurs,a machine operator can perform the required corrective actions. Thereference quantity, or the reference quantity diagram, can be aconstant, which is stored in the evaluating unit, or is selected from amultitude of constants in a data bank of the evaluating unit on thebasis of limiting conditions.

In an advantageous manner, the reference quantity and/or the referencequantity diagram can also be chronologically variable. For forming thereference values, the reference quantity and/or the reference quantitydiagram can be determined empirically in a machine status wherein thetools are not worn out.

It is also possible that the reference quantity and/or the referencequantity diagram is recursively defined, such as is derived from theparameters and/or the characteristic diagram of the historicaloperational status.

The operational status of the monitored machine component can bedetermined either continuously or at predetermined measuring intervals.

For a better explanation, reference is made in what follows to a roadmilling machine. However, the explanations analogously apply toconstruction machinery of any type.

The evaluation of the measured result preferably occurs so that thesignal picked up by the signal pickup unit is conducted to an evaluatingunit. The evaluating unit compares the picked-up signal with a presetvalue and forms a difference signal from the picked-up signal and thepreset value. It is thus possible to provide an error report which isautomated to the greatest extent. Ideally, the preset value can beempirically determined by a detection circuit, and the preset value canbe read into the evaluation circuit by the detection circuit. Duringthis, the machine operator can determine the preset values during themilling process, for example with chisels which are not worn out.

In one embodiment of this invention, a machine chassis is supported by arunning gear, wherein one or several drive motors are assigned to therunning gear, and the signal pickup unit detects the power consumptionof the drive motor. Use is made of the knowledge that changed wearconditions of the milling roller also lead to a change of the outputparameters of the drive motor.

For example, an increased drive effort can be required because ofincreased wear of the chisel. With this embodiment of this invention,the drive motors are designed as electric motors, and the signal pickupunit detects the supplied electrical current or the drive motors aredesigned as hydraulic motors. The signal pickup unit detects thehydraulic pressure in the fluid circuit assigned to the drive motor.

In one embodiment of this invention, the machine chassis is supported,at least in some areas, by at least one adjustment device, and themachine chassis can be height-adjusted, at least in some areas, by theadjustment device. A fluid under pressure is assigned to the adjustmentdevice, and the signal pickup unit detects the pressure in the fluid.

The forces occurring during milling are indirectly detected with thisarrangement. The cutting forces are low for unworn cutting chisels whichare ready to cut. The vertical portion of the cutting forces is directedopposite the force of gravity and therefore relieves the burden on theadjustment device, which otherwise would have to support the entireweight of the machine. The pressure in the fluid assigned to theadjustment device decreases proportionally with the vertical portion ofthe cutting forces. This value can also be determined by a forcemeasurement, for example with a wire strain gauge, on at least one ofthe adjustment devices or another structural component.

It is also possible for the signal pickup unit to detect the forwardprogress of the machine which can then be compared with the actualoutput parameters of the road milling machine, in particular with thedrive output required for the milling roller.

If, for example, at constant drive output the forward progress of themachine slows, then it is possible to draw conclusions regarding anincreased wear status.

A combined calculation of the following values can also be performed:vertical force direction detected by the adjustment device, for example,and horizontal force direction detected by the drive data, for example.A vector can be formed by a linear combination and the length ordirectional change can be used as evaluation criteria.

In accordance with one embodiment of invention, the signal pickup unitdetects the vibration of the machine component. This arrangement isbased on different wear conditions that also have an effect on thevibration behavior of individual machine components. This design of amachine is based on the knowledge that a uniform vibration can bedetected in view of the uniform rotatory movement of the milling roller.In the unworn state, this vibration has fixed parameters, includingamplitude and period. As a result of a tool break, for example, thevibration undergoes a sudden change toward an irregular vibration,compared with the vibration prior to the break.

With uniformly proceeding wear, the amplitude of the parameters slowlychanges in amount. Thus the irregularity or regularity of the signal isof lesser importance, or does not exist.

Thus it is preferably possible to detect the vibration by a displacementtransducer, or a speed or an acceleration sensor.

Further invention embodiments can also be distinguished if the signalpick-up unit detects the drive moment at one or several places of adrive mechanism driving the milling roller, or if the signal pickup unitdetermines the motor parameters.

In one embodiment of this invention the signal pickup unit has a pulsegenerator assigned to the milling roller. A position determination ofthe milling roller can be performed by the pulse generator. If thesignal detected by the signal pickup unit is processed together with theinformation from the pulse generator, it is possible to draw detailedconclusions regarding the position of a break-down point, for example abroken shaft.

One object of this invention is also achieved with a recognition unitthat optically detects at least a portion of the milling patterngenerated by the milling roller.

The quality of the milling pattern can be checked by the opticalrecognition unit, for example a camera. Errors due to the wear of thechisels or of a chisel break can be detected in the milling pattern. Itis also possible to use a signal pickup unit designed in the mannerdescribed above in addition to the optical recognition unit. During thisa further detailed error detection can take place.

In accordance with this invention, the recognition unit can have atleast one position sensor which detects the milling depth.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is explained in greater detail in view of an exemplaryembodiment represented in the drawings, wherein:

FIG. 1 is a lateral view of a construction machine, such as a roadmilling machine;

FIG. 2 is a schematic view of a milling roller, in a front view;

FIGS. 2 a and 2 b show the surface profile milled by the milling rollerin accordance with FIG. 2, in a schematic representation;

FIG. 3 shows a milling roller in accordance with FIG. 2, but with adefective place;

FIGS. 3 a and 3 b show the surface profile milled by the milling rollerin accordance with FIG. 3 in a schematic representation;

FIG. 4 shows the milling roller in accordance with FIG. 2, in a lateralview;

FIG. 4 a shows a vibration image taken at a road milling machineequipped with a milling roller in accordance with FIG. 4;

FIG. 5 shows the milling roller in accordance with FIG. 3, in a lateralview; and

FIG. 5 a shows a vibration image taken at a road milling machineequipped with a milling roller, in accordance with FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

The lateral view of a road milling machine shows the basic structure andthe components of the machine. A machine frame 10 is the basis for themachine, and is supported by two front running gears 11 and two rearrunning gears 12. In this case, the running gears 10 and 11 can bedriven by electric motors or hydraulic motors. These drive mechanismsoperate synchronously. It is thus sufficient to assign sensors S6 and S7for detecting the electrical current or the pressure and the speed toonly one running gear, for example 11.

A milling box 13 is attached to the machine frame 10 between the frontand rear running gears 11 and 12. The milling box 13 contains at leastone milling roller with chisel holders and chisels. The milling rolleris driven by a drive unit 16, which has a Diesel engine, wherein asensor S8 detects the transferred torque, and a sensor S10 detects otheroperating data, such as motor rpm, exhaust gas temperature, boostpressure, and the like.

A camera K is attached to the machine frame 10 between the milling box13 and the rear running gear 12, by which the milling image is detectedand recorded. The image is transferred to a video terminal BS in the cab14 of the machine and is displayed. The driver seated on the driver'sseat 15 can see the milling image on the video terminal BS arranged inthe area of the dashboard 18 and can check its status and draw aconclusion regarding its quality. A continuous check can be performed ifthe camera K and the video terminal BS are switched on during the entireoperating time of the machine. However, checking can be adjusted so thatthe devices and a display are switched on only when a request isinitiated.

Sensors S2 and S4, which detect the position of the milling roller, themilling pressure and the milling torque, are attached to the milling box13. A sensor S5 attached to the machine frame 10 above the milling box13 detects the vibrations of the milling box 13 in the direction oftravel, transversely to the direction of travel of the machine, andperpendicularly with respect to the pavement.

The machine frame 10 can be adjusted with respect to the running gears11 and 12 via a height adjustment device in order to change thepenetration depth of the milling roller in the pavement. The penetrationdepth is detected by the sensor S1. The pressure of the heightadjustment device can be detected by the sensor S9.

The removed milling material is moved away from the milling box 13 by aconveyor device, wherein the conveyor device has an endless conveyorbelt 17, one end of which is hinged to the machine frame 10 and whichcan, as shown by the sensors S11 and S12, be adjusted in height andlaterally pivoted in order to assure a transfer to a vehicle arrangedunderneath, without damage to the vehicle and/or the endless conveyorbelt 17.

The measured values detected by the sensors S1 to S12 are alsotransmitted to the cab 14 and displayed in the area of the dashboard 18.In this case, individual display elements can be assigned to allsensors, which can be activated permanently or upon request. However, acentral display device can be assigned to all sensors, on which therequested measured value is displayed, wherein the display also containsthe preset permissible range of the measured values.

The measured values can be continuously detected independently of thedisplay, and compared with the preset measured value ranges. If themeasured values lie below or above the preset measured value ranges, awarning signal can be automatically triggered, and the error situationcan be shown at the central display device.

Extensive wear of the chisels and other irregularities during operationresult in large changes in the monitored operating data and aremonitored, displayed and recognized by the driver of the road millingmachine, which then can initiate steps for error location and errorremoval. This makes the operation by the road milling machineconsiderably easier and assures that components of the machine are notoverloaded, damaged or even destroyed.

For explaining the optical milling image monitoring, a milling roller 30is first shown in the unworn state (FIG. 2) in FIGS. 2 to 3 b. As thisrepresentation shows, all chisel holders 31 are equipped withround-shaft chisels 32. The milling image A shown in FIGS. 2 a and 2 bresults from such a milling roller 30.

If a chisel is lost from the milling roller 30, for example because of atool break, the milling image B represented in FIGS. 3 a and 3 bresults. It can be seen, in particular in the enlarged detailed view inaccordance with FIG. 3 b that at the place which was not worked becauseof the loss of the chisel raised material P remains in the pavement.This can be visually detected by a camera.

The milling rollers 30 of FIGS. 2 and 3 are shown, in a lateral view, inFIGS. 4 and 5. FIGS. 4 a and 5 a represent the vibration image recordedby an appropriate sensor.

1. A road milling machine for stripping traveled surfaces by a milling having a plurality of chisels, wherein a signal pickup unit is assigned to at least one machine component involved in a work process, wherein the signal pickup unit detects an operational status of the machine component, the signal pickup unit is connected to a signal output unit via a signal processing arrangement having a machine frame (10) supported by a running gear (11, 12), at least one drive motor is assigned to the running gear, the machine frame (10) is supported at least in some areas by at least one adjustment device (20), and the machine frame (10) can be height-adjusted at least in some areas by of the adjustment device (20) for assigning a fluid under pressure to the adjustment device (20), the road milling machine comprising: the drive motors designed as hydraulic motors, and one of the signal pickup unit detecting fluctuations of the hydraulic pressure in the fluid circuit assigned to the drive motor and the signal pickup unit detecting the fluctuations of the hydraulic pressure in the fluid of the adjustment device (20), and the signal processing arrangement comparing a detected fluctuation image with a homogeneous fluctuation image of an intact milling roller and displaying deviations therefrom with a signal output arrangement.
 2. The road milling machine in accordance with claim 1, wherein the signal pickup unit detects an operational status of the machine component one of continuously and at preset measurement intervals.
 3. The road milling machine in accordance with claim 2, wherein a signal picked up by the signal pickup unit is conducted to an evaluating unit that compares a picked-up signal with a preset value and forms a difference signal from the picked-up signal and the preset value.
 4. The road milling machine in accordance with claim 3, wherein the preset value is empirically determined by a detection circuit, and the preset value is read into an evaluation circuit by the detection circuit.
 5. The road milling machine in accordance with claim 4, wherein the signal pickup unit detects power parameters including a power consumption of the drive motor.
 6. The road milling machine in accordance with claim 5, wherein a height adjustment of the adjustment device is determined by a force measurement such as of a wire strain gauge.
 7. The road milling machine in accordance with claim 6, wherein the signal pickup unit detects a forward progress of the machine.
 8. The road milling machine in accordance with claim 7, wherein a vibration is detected by one of a displacement transducer, a speed sensor and an acceleration sensor.
 9. The road milling machine in accordance with claim 8, wherein for a position determination, the signal pickup unit has a pulse generator assigned to the milling roller.
 10. The road milling machine in accordance with claim 8, wherein the signal pickup unit detects at least one motor parameters parameter.
 11. The road milling machine in accordance with claim 10, having a milling roller with a plurality of chisels driven by a drive arrangement, and the signal pickup unit detects a drive torque at least at one location of the drive arrangement.
 12. The road milling machine in accordance with claim 1, wherein a signal picked up by the signal pickup unit is conducted to an evaluating unit that compares a picked-up signal with a preset value and forms a difference signal from the picked-up signal and the preset value.
 13. The road milling machine in accordance with claim 12, wherein the preset value is empirically determined by a detection circuit, and the preset value is read into an evaluation circuit by the detection circuit.
 14. The road milling machine in accordance with claim 1, wherein the signal pickup unit detects power parameters including a power consumption of the drive motor.
 15. The road milling machine in accordance with claim 1, wherein a height adjustment of the adjustment device is determined by a force measurement such as of a wire strain gauge.
 16. The road milling machine in accordance with claim 1, wherein the signal pickup unit detects a forward progress of the machine.
 17. The road milling machine in accordance with claim 1, wherein a vibration is detected by one of a displacement transducer, a speed sensor and an acceleration sensor.
 18. The road milling machine in accordance with claim 1, wherein for a position determination, the signal pickup unit has a pulse generator assigned to the milling roller.
 19. The road milling machine in accordance with claim 1, wherein the signal pickup unit detects at least one motor parameter.
 20. The road milling machine in accordance with claim 1, having a milling roller with a plurality of chisels driven by a drive arrangement, and the signal pickup unit detects a drive torque at least at one location of the drive arrangement. 